Here the problem - 904 with a 273 2bbl
I changed the radiator in my car - replaced the lost tranny oil - The tranny is now slipping between 2nd and drive. Some times long slip before the gear locks in sometimesi have to let my foot off the gas and it goes in. no Problem with R 3 or 2

Kick down rods are good and connected all bushings are good as well

was fine before I changed the radiator.
Fluid level is fine checked in N while car was running.


Any ideas of what it could be? Is it time for a new tranny?
could the valve body be dirty? possible dirty filter?
Any advice would be helpful.

 

Possibly sticking governor or malfunctioning valve body, but when you say it was fine before the rad change I think "what changed?".
Could make guesses but I would drop pan change filter with new fluid and maybe get a transmission flush if you have a shop you can trust to do it properly on an old style transmission. Really sounds like a pressure problem from a pinched or restricted cooler line.

 

What kind of fluid did you put it ? I would not flush the trans. Remove the pan and change the filter and the fluid and adjust the band.. If it still has problems ? it is time for an overhaul. one of the clutch packs is worn out

 

no kinks in the lines all steel lines and originals